For now, I've been adding an opening_hours tag on the barrier nodes on the entrance lanes (and on the entrance lanes themselves) for the Atlanta express roads, mainly so that the information gets captured and is available in OSM. I haven't touched this on the Selmon Expressway because it has a more complex reversal schedule. I have specifically avoided putting opening_hours on barrier nodes on the exit lanes, though, because you can exit even after the barriers on the entrance lanes go down.

Another way to approach this might be to utilize route relations. However, this is significantly more complex.

I've started a discussion on the OSM Tagging mailing list, which I invite everyone to join in on: